Empirical threshold values for quantitative trait mapping.

Drought stress results in significant crop yield losses. Comparative transcriptome analysis between tolerant and sensitive species can provide insights into drought tolerance mechanisms in jute. We present a comprehensive study on drought tolerance in two jute species—a drought tolerant species (Corchorus olitorius L., GF) and a drought sensitive species (Corchorus capsularis L., YY). In total, 45,831 non-redundant unigenes with average sequence length of 1421 bp were identified. Higher numbers of differentially expressed genes (DEGs) were discovered in YY (794) than in GF (39), implying that YY was relatively more vulnerable or hyper-responsive to drought stress at the molecular level; the two main pathways, phenylpropanoid biosynthesis and peroxisome pathway, significantly involved in scavenging of reactive oxygen species (ROS) and 14 unigenes in the two pathways presented a significant differential expression in response to increase of superoxide. Our classification analysis showed that 1769 transcription factors can be grouped into 81 families and 948 protein kinases (PKs) into 122 families. In YY, we identified 34 TF DEGs from and 23 PK DEGs, including 19 receptor-like kinases (RLKs). Most of these RLKs were downregulated during drought stress, implying their role as negative regulators of the drought tolerance mechanism in jute.

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Transcriptome Analysis of Two Species of Jute in Response to Polyethylene Glycol (PEG)- induced Drought Stress

Fine mapping QTLs and identifying candidate genes for cotton fibre-quality and yield traits would be beneficial to cotton breeding. Here, we constructed a high-density genetic map by specific-locus amplified fragment sequencing (SLAF-seq) to identify QTLs associated with fibre-quality and yield traits using 239 recombinant inbred lines (RILs), which was developed from LMY22 (a high-yield Gossypium hirsutumL. cultivar) × LY343 (a superior fibre-quality germplasm with G. barbadenseL. introgressions). The genetic map spanned 3426.57 cM, including 3556 SLAF-based SNPs and 199 SSR marker loci. A total of 104 QTLs, including 67 QTLs for fibre quality and 37 QTLs for yield traits, were identified with phenotypic data collected from 7 environments. Among these, 66 QTLs were co-located in 19 QTL clusters on 12 chromosomes, and 24 QTLs were detected in three or more environments and determined to be stable. We also investigated the genomic components of LY343 and their contributions to fibre-related traits by deep sequencing the whole genome of LY343, and we found that genomic components from G. hirsutum races (which entered LY343 via its G. barbadense parent) contributed more favourable alleles than those from G. barbadense. We further identified six putative candidate genes for stable QTLs, including Gh_A03G1147 (GhPEL6), Gh_D07G1598 (GhCSLC6) and Gh_D13G1921 (GhTBL5) for fibre-length QTLs and Gh_D03G0919 (GhCOBL4), Gh_D09G1659 (GhMYB4) and Gh_D09G1690 (GhMYB85) for lint-percentage QTLs. Our results provide comprehensive insight into the genetic basis of the formation of fibre-related traits and would be helpful for cloning fibre-development-related genes as well as for marker-assisted genetic improvement in cotton.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/pbi.13237

Identification of candidate genes for key fibre‐related QTLs and derivation of favourable alleles in Gossypium hirsutum recombinant inbred lines with G. barbadense introgressions

Flavonoids are important components that confer upon tea plants a unique flavour and health functions. However, the traditional breeding method for selecting a cultivar with a high or unique flavonoid content is time consuming and labour intensive. High-density genetic map construction associated with quantitative trait locus (QTL) mapping provides an effective way to facilitate trait improvement in plant breeding. In this study, an F1 population (LJ43×BHZ) was genotyped using 2b-restriction site-associated DNA (2b-RAD) sequencing to obtain massive single nucleotide polymorphism (SNP) markers to construct a high-density genetic map for a tea plant. Furthermore, QTLs related to flavonoids were identified using our new genetic map. A total of 13,446 polymorphic SNP markers were developed using 2b-RAD sequencing, and 4,463 of these markers were available for constructing the genetic linkage map. A 1,678.52-cM high-density map at an average interval of 0.40 cM with 4,217 markers, including 427 frameset simple sequence repeats (SSRs) and 3,800 novel SNPs, mapped into 15 linkage groups was successfully constructed. After QTL analysis, a total of 27 QTLs related to flavonoids or caffeine content (CAF) were mapped to 8 different linkage groups, LG01, LG03, LG06, LG08, LG10, LG11, LG12, and LG13, with an LOD from 3.14 to 39.54, constituting 7.5% to 42.8% of the phenotypic variation. To our knowledge, the highest density genetic map ever reported was constructed since the largest mapping population of tea plants was adopted in present study. Moreover, novel QTLs related to flavonoids and CAF were identified based on the new high-density genetic map. In addition, two markers were located in candidate genes that may be involved in flavonoid metabolism. The present study provides valuable information for gene discovery, marker-assisted selection breeding and map-based cloning for functional genes that are related to flavonoid content in tea plants.

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High-density SNP linkage map construction and QTL mapping for flavonoid-related traits in a tea plant (Camellia sinensis) using 2b-RAD sequencing.

We constructed the first high-quality and high-density genetic linkage map for an interspecific BIL population in cotton by specific-locus amplified fragment sequencing for QTL mapping. A novel gene GhPIN3 for plant height was identified in cotton. Ideal plant height (PH) is important for improving lint yield and mechanized harvesting in cotton. Most published genetic studies on cotton have focused on fibre yield and quality traits rather than PH. To facilitate the understanding of the genetic basis in PH, an interspecific backcross inbred line (BIL) population of 250 lines derived from upland cotton (Gossypium hirsutum L.) CRI36 and Egyptian cotton (G. barbadense L.) Hai7124 was used to construct a high-density genetic linkage map for quantitative trait locus (QTL) mapping. The high-density genetic map harboured 7,709 genotyping-by-sequencing (GBS)-based single nucleotide polymorphism (SNP) markers that covered 3,433.24 cM with a mean marker interval of 0.67 cM. In total, ten PH QTLs were identified and each explained 4.27–14.92% of the phenotypic variation, four of which were stable as they were mapped in at least two tests or based on best linear unbiased prediction in seven field tests. Based on functional annotation of orthologues in Arabidopsis and transcriptome data for the genes within the stable QTL regions, GhPIN3 encoding for the hormone auxin efflux carrier protein was identified as a candidate gene located in the stable QTL qPH-Dt1-1 region. A qRT-PCR analysis showed that the expression level of GhPIN3 in apical tissues was significantly higher in four short-statured cotton genotypes than that in four tall-statured cotton genotypes. Virus-induced gene silencing cotton has significantly increased PH when the expression of the GhPIN3 gene was suppressed.

QTL analysis and candidate gene identification for plant height in cotton based on an interspecific backcross inbred line population of Gossypium hirsutum × Gossypium barbadense.

Genetic mapping and quantitative trait locus (QTL) detection are powerful methodologies in plant improvement and breeding. White jute (Corchorus capsularis L.) is an important industrial raw material fiber crop because of its elite characteristics. However, construction of a high-density genetic map and identification of QTLs has been limited in white jute due to a lack of sufficient molecular markers. The specific locus amplified fragment sequencing (SLAF-seq) strategy combines locus-specific amplification and high-throughput sequencing to carry out de novo single nuclear polymorphism (SNP) discovery and large-scale genotyping. In this study, SLAF-seq was employed to obtain sufficient markers to construct a high-density genetic map for white jute. Moreover, with the development of abundant markers, genetic dissection of fiber yield traits such as plant height was also possible. Here, we present QTLs associated with plant height that were identified using our newly constructed genetic linkage groups. An F8 population consisting of 100 lines was developed. In total, 69,446 high-quality SLAFs were detected of which 5,074 SLAFs were polymorphic; 913 polymorphic markers were used for the construction of a genetic map. The average coverage for each SLAF marker was 43-fold in the parents, and 9.8-fold in each F8 individual. A linkage map was constructed that contained 913 SLAFs on 11 linkage groups (LGs) covering 1621.4 cM with an average density of 1.61 cM per locus. Among the 11 LGs, LG1 was the largest with 210 markers, a length of 406.34 cM, and an average distance of 1.93 cM between adjacent markers. LG11 was the smallest with only 25 markers, a length of 29.66 cM, and an average distance of 1.19 cM between adjacent markers. ‘SNP_only’ markers accounted for 85.54% and were the predominant markers on the map. QTL mapping based on the F8 phenotypes detected 11 plant height QTLs including one major effect QTL across two cultivation locations, with each QTL accounting for 4.14–15.63% of the phenotypic variance. To our knowledge, the linkage map constructed here is the densest one available to date for white jute. This analysis also identified the first QTL in white jute. The results will provide an important platform for gene/QTL mapping, sequence assembly, genome comparisons, and marker-assisted selection breeding for white jute.

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High-density genetic map construction and QTLs identification for plant height in white jute (Corchorus capsularis L.) using specific locus amplified fragment (SLAF) sequencing.

The invention belongs to the field of plant molecular biology, and particularly relates to a method for efficiently and stably extracting deoxyribonucleic acid (DNA) from mature kenaf laminas. According to the invention, a method for extracting genome DNA from kenaf laminas by a cetyltrimethyl ammonium bromide (CTAB) method is improved and optimized on the basis of a traditional kenaf genome DNA extraction method by combining with the characteristic that the mature kenaf laminas contain polysaccharide and polyphenol. The kenaf genome DNA obtained by applying the method for efficiently and stably extracting the DNA from the mature kenaf laminas has clear strips and do not have tailings; OD260/OD280 is 1.7-1.9; enzyme digestion is complete; the quality and the yield of the kenaf genome DNA obtained by applying the method for efficiently and stably extracting the DNA from the mature kenaf laminas are higher than that of the kenaf genome DNA obtained by applying an improved sodium dodecyl sulfonate (SDS) method. The kenaf genome DNA can be used for amplifying chloroplast DNA and mitochondria DNA. A working foundation is laid for further developing researches on genomics of kenaf and bast-fibre plants thereof and subcellular genomics.

Method for extracting deoxyribonucleic acid (DNA) from mature kenaf laminas

Jute leaf health tea and preparation method thereof

The invention relates to a method for breeding a cytoplasmic male sterile line of quality disease-resistant photo periodical insensitive hibiscus cannabinus. The method relates to integrating high quality, disease resistance and photo periodical insensitive performance and other outstanding properties to hibiscus cannabinus; the cytoplasmic male sterile line of hibiscus cannabinus is used as a female parent, the quality, disease-resistant and photo periodical insensitive hibiscus cannabinus is used as a male parent; the female parent and the male parent are subjected to saturation hybridization to obtain a hibiscus cannabinus cytoplasmic male sterile line which has the growth characteristics of photo periodical insensitive performance, high quality, disease resistance, growth stability, high economy and high combining ability. The hibiscus cannabinus sterile line bred by the method can effectively utilize the advantages of photo periodical insensitive performance and hybrid, the hibiscus cannabinus planting area can be widely expanded to international and national tropical zones with low latitude for annual planting, and therefore, the international core competitiveness and original innovation level of domestic cytoplasmic can be greatly increased.

Breeding method of cytoplasmic male sterile line of quality disease-resistant photo periodical insensitive hibiscus cannabinus

White jute ( Corchorus capsularis L.) is recognized as an important industrial raw material fibre crop owing to its elite characters. However, little information is known about its molecular basis and genomics. In this study, a complementary DNA library of white jute was constructed and expressed sequence tags (ESTs) were characterized. The titers of original and amplified libraries were 2.32 × 10 7  and 1.07 × 10 9 pfu/mL, respectively. The recombinant frequency was 98.3% in the library. Most of the sequences ranged from 500 to 1500 bp with an average length of 750 bp. Results show 203 (73%) ESTs exhibited significant similarity with known or putative functional nucleotide sequences in the GenBank databases. Cluster analysis allowed the identification of 61 unique sequences. These genes were classified into six types by Gene Ontology (GO) annotation. The results also indicated that unigenes of  C. capsularis have higher homology to Populus trichocarpa , Ricinus communis and Corchorus olitorius . This report will provide a valuable resource for the further investigations in the gene cloning, transcription or expression for white jute. Key words: White jute, Corchorus capsularis, cDNA library, construction, ESTs, analysis.

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Lin Peiqing

Papers

High-density genetic map construction and QTLs identification for plant height in white jute (Corchorus capsularis L.) using specific locus amplified fragment (SLAF) sequencing.

Method for extracting deoxyribonucleic acid (DNA) from mature kenaf laminas

Jute leaf health tea and preparation method thereof

Breeding method of cytoplasmic male sterile line of quality disease-resistant photo periodical insensitive hibiscus cannabinus

Construction of a full-length cDNA library and analysis of expressed sequence tags in white jute (Corchorus capsularis L.)